Electronic weft detector for looms



Nov. 25, 1947. v. F. SEPAVICH EI'AL 2,431,429

ELECTRONIC WEFT DETECTOR FOR LOOMS Filed June 6, 1946 INVENTOR VICTOR F. SEPA V/GH JOHN G. MANOOG O/ww T ATTORNEY Patented Nov. 25, 1947 ELECTRONIC WEFT DETECTOR FOR LOOMS Victor F. Sepavich and John C. Manoog, Worcester, Mass, assignors to Crompton & Knowles Loom Works, Worcester, Mass, a corporation of Massachusetts Application June 6, 1946, Serial No. 674,921

10 Claims.

Thi invention relates to improvements in weft detectors for looms and it is the general object of the invention to provide an electric detecting circuit utilizing an electronic tube which is under control of the weft detector.

Certain types of electric weft detectors employ two insulated electrodes or conducting fingers for engagement with the ferrule of the depleted bobbin. Heretofore it has been customary to use a single circuit including a source, the electrodes and ferrule, and the loom controlling solenoid. In such circuits, however, the current at the ferrule is relatively large and results in arcing which is detrimental to the yarn engaging surfaces of the fingers. It is an important object of our present invention to separate the solenoid circuit from the detector circuit and control it by electronic circuit means including a tube the grid of which is connected to the weft detector. The current required for control of the grid is very small and causes no arcing when the fingers engage the ferrule at the time of indication of weft exhaustion,

It is not practicable to inclose all parts of an electric weft detecting system, inasmuch as some parts of it must be exposed for correct operation, such for instance as the aforesaid fingers. These parts can therefore be touched by the weaver or loom fixer and should operate at such low voltages as will cause no shock when touched. It is another object of our invention to control the grid of the electronic tube by a detector circuit operatin at a low voltage and under such conditions that no danger of shock exists.

With these and other objects in view which will appear as the description proceeds, our invention resides in the combination and arrangement of parts hereinafter described and set forth.

In the accompanying drawings, wherein a convenient embodiment of our invention is set forth,

Fig 1 is a plan view of a weft detector havin electrodes thereof in contact with the ferrule of a depleted bobbin, and

Fig. 2 is a diagram of the circuits used with the detector shown in Fig. 1.

Referring particularly to Fig. 1, we have shown a loom carried support it] on which is mounted a detector D bolted to the support as at l I. The detector includes a body l2 made of insulating material in which are slidably mounted right and left hand electrodes or detector fingers l3 and I4. respectively. These fingers are urged rearwardly by small compression springs l5 which permit forward yielding of the detector fingers. The detector D is provided with right and left hand binding posts IB and IT, respectively, which are in electric contact with the corresponding detector fingers. The bobbin B is provided with a metal ferrule I8 ordinarily covered by Weft not shown. During those detecting operations of the loom in which there is sufllcient weft on the bobbin the ferrule will be covered, but as weavin continues the ferrule is uncovered and eventually establishes electric contact with the fingers l3 and M.

The loom with which the invention is used will ordinarily have some mechanism called into action by a solenoid. It is not thought necessary to illustrate this mechanism since various forms are well known. The loom will have a circuit for the solenoid indicated at the left of Fig. 2 supplied with power by the secondary 20 of a transformer T and including a switch 2| under control of a relay 22. When the latter is energized, as will be described hereinafter, the following solenoid circuit is closed: ground G, wire 23, winding 20, wire 24, solenoid S. wire 25, switch 2| and wire 26 back to ground. This circuit may operate at 12 volts, as has been common practice in the past, or at a higher voltage, provided the solenoid is wound for the higher voltage.

A second transformer T has secondary windings 30 and 3|, the latter supplying electric power at low voltage and the former at a higher voltage. The primaries of both transformers may be connected to lines L and L of a source of alternating electric current.

An electronic tube E having a plate P, grid 32, cathode C and filament F is provided for the detector and relay circuits. When current can flow through the tube E the following relay circuit is energized: ground G, wires 35 and 36, winding 30, wires 31 and 38, relay 22, wires 39 and Oil. plate P through the tube to the cathode C and wires 4t, 42 and 43 to the ground. Connected in parallel with the relay 22 is a resistance R and a condenser 45. The resistance and condenser are in series with each other and constitute a local normally idle closed circuit through relay 22.

The detector circuit is supplied with low voltage direct current by a rectifier 44 which is connected across the winding 3| as follows: rectifier 44, wires 46 and 41, winding 3i, and wires 48 and 49 back to the rectifier. When thus connected the full wave rectifier is a source of uni-directional current which energizes the following detector circuit: ground G, wire 35, wire 50 to the positive side of the rectifier. the rectifier, wire 5i connected to the negative side of the rectifier, resistance R, wire 52, junction 53, wire 54, junction 55, wire 56,

finger I3, feeler body [2 as a high resistance R2, finger l4, and wire 51 back to the ground. When there is sufficient yarn on the ferrule it the fingers will not be electrically connected except by resistance R2, which, together with resistance R, determines the bias of the grid 32 by reason of wire 59 connecting the grid to the junction 53. This bias will ordinarily be such as to prevent firing of the tube.

The detector D is in parallel with a second condenser 60 connected by wire ii to junction 55 and by wire 82 to the ground. This condenser under normal conditions is parallel with the resistance R2 and is connected to the detector circuit between the resistances R and R2. The condenser is normally charged, but is discharged whenever the fingers engage the bare ferrule it. After discharge, condenser 60 will ordinarily require an appreciable time for recharging, this time usually extending beyond the break of contact between ferrule l8 and the detector fingers which occurs at the conclusion of the detecting operation.

The cathode and filament circuit is as follows: ground G, wire 35, wire 48, winding 3|, wire 41, wire 65, filament F, wire 66 connecting with the cathode by wire ll, and wires 42 and 43 back to the ground G. This cathode circuit determines the normal bias of the cathode which is so related to the grid 32 under ordinary conditions that current cannot flow through the tube.

In operation under normal conditions relay 22 will be deenergized and switch 2| will be open, condenser 45 will be in a state of discharge, and condenser 60 will be charged. These conditions remain until the ferrule l 8 is depleted and engages the fingers I 3 and H, whereupon the resistance R2 is short-circuited and condenser 60 is discharged to the ground. The potential of the grid 32 is thus altered and current flows through the tube and relay circuit already described, thereby energizing the relay 22 and also charging the condenser 45. The latter may for instance be of 8 microfarad capacity and when th relay circuit through the tube is interrupted by alternation of the current in winding 30 condenser 45 will discharge through the relay and resistance R to maintain the relay energized sufliciently long so that solenoid 30 can be effectively energized.

Condenser 60 may be of a .01 microfarad capacity and after the detector contact is broken by movement of the ferrule away from the fingers i3 and It the rectifier will charge the condenser 60, and during the period of recharging the grid 32 will remain in such electric condition as to permit current to flow through the tube E for a long enough time to cause complete energization of the relay and solenoid. The resistances R and R may be respectively 1,000 and 25,000 ohms, while the resistance R2 of the body of the detector D will be relatively very much higher, such as of the order of one megohm or more. The winding 30 may supply electric power at approximately 110 volts and the relay 22 may have a resistance of approximately 2500 ohms.

The detector D will have a small capacitance. which, however, will be much smaller than that of condenser 60. Variations in the condenser value of the detector will therefore not materially affect the capacitance of the detector circuit, since the two capacitances are in parallel.

From the foregoing it will be seen that we have provided a simple form of electric weft detector employing an electronic tube the grid of which is controlled by a detector circuit operating at such a low voltage that risfic of shock to the attendant is eliminated. It wil be noted that windings 30 and 3| have a common ground through wire 35. It will also be seen that the rectifier under ordinary conditions continuously maintains the grid connected to the negative side of it in such electric condition as to prevent flow of electric current through the tube E. While we have shown a relay 22 as being independent of the solenoid S we do not wish necessarily to be limited to this arrangement and it is suflicient if plate current flowing through the-tube energizes an electromagnetic device to initiate a change in loom operation.

Having thus described our invention it will be seen that changes and modifications may be made therein by those skilled in the art without departing from the spirit and scope of the invention and we do not wish to be limited to the details herein disclosed, but what we claim is:

1. In an electric weft detecting system for a loom having an electromagnetic device which when energized effects a change in loom operation, an electric weft detector having two normally insulated electrodes which are electrically connected upon indication of weft exhaustion, a source of relatively low potential electric power, a source of relatively high potential electric power, an electronic tube having a plate and grid, a detector circuit including the low potential source and detector connected to the grid and normally enabling the latter to prevent flow of current through the tube, a plate circuit including said high potential source, device and plate tending normally to energize the device by current flowing through the tube but prevented from doing so by the grid, said detecting circuit efiective when the electrodes of the detector are electrically connected to change the grid electrically so that current can flow through the tube from said high potential source to energize said device, and a grounded common connection between said sources of electric power.

2. In an electric weft detecting system for a loom having an electromagnetic device which when energized effects a change in loom operation, an electric weft detector having two normally insulated electrodes which are electrically connected upon indication of weft exhaustion, an electronic tube having a plate and grid, a source of relatively low potential alternating current electric power, a rectifier connected across said source, a detector circuit including said rectifier and detector normally maintaining the grid in such electric condition as to prevent flow of current through the tube, a second source of relatively high potential alternating current electric power, tube circuit means containing said second source, device and tube normally tending to energize said device but prevented from doing so by said grid, the electrodes of the detector when electrically connected altering the detector circuit to effect an electrical change in the grid enabling said tube circuit means to cause current to flow through said device, and a grounded common connection between said rectifier and said second source.

3. In an electric weft detecting system for a loom having an electromagnetic device which when energized effects a change in loom operation, an electric weft detector having two normally insulated electrodes which are electrically connected upon indication of weft exhaustion, an electronic tube having a plate, grid and cathode, a. source of relatively low potential alternating current electric power, a rectifier connected across said source, cathode circuit means including said source connected to said cathode, detector circuit means including said rectifier and detector connected to the grid and normally enabling the latter to prevent flow of current through the tube when the electrodes of the detector are electrically disconnected from each other, a source of relatively high alternating current electric power, tube circuit means including the latter source, device and tube normally tending to energize said device but prevented from doing so by the grid, the electrodes of the detector when electrically connected effecting a change in the detecting circuit which alters the electric condition of the grid in such manner that current can flow through said tube circuit means to energize said device by power derived from the second source, and a common grounded connection between said sources and rectifier.

4. In an electric weft detecting system for a loom having an electromagnetic device which when energized effects a change in loom operation, an electric weft detector having two normally insulated electrodes which are electrically connected upon indication of weft exhaustion, two sources of alternating current electric power, one of said sources supplying electric power at relatively low voltage and the other source supplying electric power at relatively high voltage, an electronic tube having a plate and grid, detector circuit means deriving power from said one source and including the detector and connected to the grid and effective to enable the latter to prevent flow of current through the tube when said electrodes are electrically disconnected from each other, and a plate circuit including said other source, device and tube tending normally to energize said device but prevented from doing so by the grid, said electrode when electrically connected altering the detector circuit to effect a change in the electric condition of the grid to enable said other source to cause current to flow through the tube and energize said device.

5. In an electric weft detecting system for a loom having an electromagnetic device which when energized effects a change in loom operation, an electric weft detector having two normally insulated electrodes which are electrically connected upon indication of weft exhaustion, a source of relatively low voltage electric power, an electronic tube having a plate and grid, an electric condenser, detector circuit means deriving power from said low voltage source and including said detector and condenser and connected to the grid and normally enabling the latter to prevent flow of current through the tube when said electrodes are electrically disconnected, a second source oi relatively high voltage electric power, and plate circuit means including said second source, device, and tube normally tending to energize said device but prevented from doing so by the grid, said condenser being normally charged and said detector effective when the electrodes thereof are electrically connected to discharge said condenser and effect a change in the electric condition of the grid to permit current from said second source to flow through the tube and energize said device.

6. In an electric weft detecting system for a loom having an electromagnetic device which when energized effects a change in loom operation, an electric weft detector having two normally insulated electrodes which are electrically connected upon indication of weft exhaustion, an

electronic tube having a plate and grid, a source of relatively low potential direct current, an electric condenser, detector circuit means including said source, said detector and condenser normally charging the latter and connected to the grid and normally enabling the latter to prevent current from flowing through the tube when said electrodes are electrically disconnected and the condenser is charged, a second source of electric power of relatively high potential, and plate circuit means including said second source, device and tube normally tending to energize said device but prevented from doing so by said grid, said electrodes when electrically connected eiiecting discharge of said condenser and altering the electric condition of the grid in such manner as to permit current from said second source to flow through the tube and energize said device.

7. In an electric weft detecting system for a loom having an electromagnetic device which when energized effects a, change in loom operation, an electric weft detector having two normally insulated electrodes which are electrically connected upon indication of weft exhaustion, an electronic tube having a plate and grid, a source of electric power, grounded detector circuit means including said source and detector connected to the grid and normally enabling the latter to prevent fiow of current through the grid when said electrodes are electrically disconnected, and electric circuit means having a source of electric power independent of the first named source and including the device and tube and normally tending to energize said device but prevented from doing so by the grid, said electrodes when electrically connected effecting a change in the electric condition of the grid to enable said electric circuit means to cause current to flow through the tube and energize the device.

8. In an electric weft detecting system for a m having an electromagnetic device which when energized effects a change in loom operation, an electric weft detector having two normally insulated electrodes which are electrically connected upon indication of weft exhaustion, an electronic tube having a plate and grid, a source of relatively low voltage electric power, an electric condenser, grounded detector circuit means including said source, detector and condenser normally maintaining the latter charge and connected to the grid and enabling the latter to prevent fiow of current through the tube when said electrodes are electrically disconnected, a source of relatively high voltage electric power, and circuit means including the last named source, said device and tube normally ineffective to energize said device due to the normal electric condition of the grid, said electrodes when electrically connected discharging said condenser and altering said detector circuit means in such manner that current can flow through said tube, whereupon the second named source causes energizatlon of said device.

9. In an electric weft detecting system for a loom having an electromagnetic device which when energized effects a change in loom operation, on electric weft detector having two normally disconnected electrodes which are electrically connected upon indication of weft exhaustion, an electronic tube having a plate and grid, a source of relatively low potential electric power, 5, normally charged condenser, detector circuit means including said source, detector and condenser connected to the grid and normally enabling the latter to prevent flow of current through the tube I 7 when said electrodes are electrically disconnected, one of said electrodes, one side of the condenser and one side of said source being grounded, a second source of relatively high potential electric power, a device circuit including said second source, said device and tube normally ineffective to energize said device due to the electric condition of the grid, said electrodes when electrically connected effecting discharge of the condenser and altering the electric condition of the grid in such manner as to permit electric current from said second source to flow through a tube and said device to energize the latter.

10. In an electric weft detecting system for a loom having a normally deenergized electric device which when energized eifects a change in loom operation, an electric weft detector normally in such condition that electric current cannot flow therethrough but through which electric current can pass when the detector indicates weft exhaustion, an electronic tube including a plate and grid, a relatively low potential source of elec tric power one side of which is grounded, a normally charged condenser, detector circuit means including said source, detector and condenser and connected to the grid and normally enabling the latter to prevent flow 01 electric current through the tube when the detector is unable to pass electric current, one side of said condenser being grounded and the other side of the condenser being connected to the detector in such manner as to be grounded when the detector indicates weft exhaustion, a. source of relatively high electric potential, and device circuit means including said second source. said device and tube effective to energize said device when said detector connects said other side of the condenser to the ground.

VICTOR F. SEPAVICH. JOHN C. MANOOG. 

